All but three species of bats are vampire bats

But the truth is that out of over 1200 bat species,only three are vampire bats.Out of these three, only one prefers the blood of mammals,and even these bats mostly feed on cattle.Maybe that still doesn't seem so great,but vampire bats can be a great help to humans.A chemical known as desmoteplase found in vampire bat saliva helps break down blood clots,and is being tested by recovering stroke victims.